This invention relates in general to adjustable wrenches and in particular, to an adjustable wrench having multiple arched gripping members on the drive faces of the jaws of the adjustable wrench.
Often the work environment for a user of an adjustable wrench is a small space and therefore requires multiple cycles of placing the wrench on the nut, turning a small angle, removing the wrench and readjusting. Usually, a worm gear-rack mechanism in the head structure of the wrench is disposed in driving relation with gear teeth that are provided on the movable jaw. While the main advantage of an adjustable jaw wrench is the ability to rotate variable size bolts or nuts, some of the disadvantages involve the tradeoff between a tight fit of the wrench faces to the nut flats versus having too wide a separation of faces in which case the wrench faces slip off the nut as torque is applied. Additionally, when a great amount of torque is applied, the adjustable jaw tends to back off the object being gripped. Often, for both of these cases the nut is damaged as a result of rounding of the corners and the user may be injured.
Several solutions to increase the torque that may be applied to the nut or bolt are discussed within. One group of solutions focus on providing a greater wrench face resistance to adjustment once a setting has been set on an adjustable face. For example, by placing a spring between the worm gear and a side of the slot opposite the fixed jaw of the wrench, the natural tension within the spring will provide a force to maintain the adjustable jaw in the correct position. Another approach has included providing a locking means, such as a nut threaded on to the exterior of the wrench in order to lock the position of the adjustable jaw once adjustment has been made.
Another group of solutions has focused on increasing the surface contact of the wrench face to the nut or bolt. For example, U.S. Pat. No. 5,239,899 for a Wrench with Inclined Drive Faces teaches a single main drive face 55 shown on each jaw and having a single notch on each drive face for retaining a nut.
For the foregoing reasons there exists a need for an adjustable wrench that has an increased surface area on the jaws for gripping the nut or bolt. There is a need for an adjustable wrench that has a high angle of approach. There is also a need for an adjustable wrench that locks on the nut under torque and that drives on the nut planes when the jaw is tight or loose. For the foregoing reasons there exists a need for an adjustable wrench that is safer for the user and protects the nut corners from rounding.
In this invention an adjustable wrench has a handle with a stationary member and a movable member on a front end of the handle. The stationary member and the movable member define an opening for engaging a nut. The opening is defined by a stationary jaw face on the upper or stationary member and a movable jaw drive face on the lower or movable member. On each of the stationary drive face and the movable drive face are a plurality of arc planes, usually four, that function together as gripping members that are provided to assist in gripping the flats of a nut.
The gripping members are preferably arched in cross-section and run across the width of the jaw drive face, although gripping members that traverse a portion of the width of the jaw drive face could be used. The gripping members may be of equal size or possess a progressive pitch wherein the size of each gripping member progressively decreases from a front edge to a rear edge or vice versa. It is understood that certain wrench sizes are meant for driving a certain range of nut or bolt sizes. Pitch sizes for gripping members can be selected that will maximize that amount of surface area driving on the nut that are appropriate for the size wrench desired. Similarly, the gripping members may either be symmetrical or asymmetrical wherein a forward or rearward portion of an individual gripping member has a different curvature than the remainder of the gripping member. Other variations for the gripping members include a two radius bias or a three radius bias for the cross-section of each individual gripping member.